This invention relates in general to projectiles and in particular to an improved rotating band for projectiles which are rammed into a forcing cone of a hot gun during loading. A particular feature is improved operation in gun firing solutions requiring elevated barrel angles.
The purpose of the rotating band are to hold the projectile in the forcing cone until firing and to spin the projectile as it leaves the gun barrel. Spinning the projectile is desired because it gives the projectile added stability and range while in flight. The rotating band also acts as a seal to keep the propellant gases from escaping past the projectile, resulting in more energy being delivered to the projectile at firing.
The metallic rotating bands which were first used were heavy and caused excessive wear on the gun barrel. Many variations using thermoplastic material have been tried to solve the problems associated with metallic bands. The plastic rotating bands were lighter and softer but posed additional problems. They would either slip from the projectile during flight, thereby reducing the spin rate and range, or would fall to retain the projectile in the forcing cone during loading. Discarding rotating bands, such as U.S. Pat. No. 3,744,426 to Butler, which were designed to break off after exiting the gun barrel, solved the in-flight stability problems. However, the materials and design used in the Butler patent and others were inadequate to solve the retention problem. High temperatures in the gun barrel, approaching 575.degree. F., would simply melt the plastic bands, causing the projectile to fall out of the forcing cone when the gun barrel was elevated.
The plastic rotating bands were also very rigid. When the projectile was rammed into the forcing cone at approximately 24 feet per second, the plastic bands would either crack, become unseated, or cause the projectile to rebound. If the rotating band cracked or became unseated from the projectile, the effectiveness of the seal would decrease and the range of the projectile would be limited. Therefore, it became necessary to design a plastic rotating band which would solve the above problems without sacrificing the performance of the projectile. The subject invention meets these criteria.